How do I get rid of filamentous algae?

newgen(9 Central California)June 1, 2011

They stick to the walls of the pond, they clog up my pump filter and generally just look ugly. They even grow around the roots of the elephant ears.


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String algae. You don't completely. and the fish can eat it sometimes. It helps catch smaller crud.

Remove with a toilet brush which will catch most of it (along with smaller crud)and scrub it off surfaces. Its easy, (unless you have a large pond) amd satisfying. You can sling most of the stuff off the toilet brush.

    Bookmark   June 1, 2011 at 12:48PM
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newgen(9 Central California)

Toilet brush to scrape the wall, that's a great idea! I've been scooping it up with a aquarium fish net. I only have 2 gold fish and a bunch of frogs, so they can't really eat much of that stuff.


    Bookmark   June 1, 2011 at 2:09PM
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sleeplessinftwayne(z4-5 IND)

Hydrogen peroxide is an excellent control for many kinds of algae.A UV light is even better.

Here is a link that might be useful: Algae FAC

    Bookmark   June 2, 2011 at 4:14PM
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buyorsell888(Zone 8 Portland OR)

A UV doesn't work on string algae.

Some algae carpeting the liner is good. The longest stuff can be twirled out with a toilet brush but scrubbing the liner isn't a good idea.

    Bookmark   June 3, 2011 at 11:38AM
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newgen(9 Central California)

buyorsell: I don't expect to be able to completely rid my pond of the algae, so there'll be some leftover afterwards. Just curious, why do you say that scrubbing the liner isn't a good idea?

    Bookmark   June 3, 2011 at 3:53PM
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sleeplessinftwayne(z4-5 IND)

Sigh. But Hydrogen peroxide does work on string algae. Read the link.
String algae will spread from isolated areas by casting free into the water which does get affected by a UV.

    Bookmark   June 3, 2011 at 10:11PM
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buyorsell888(Zone 8 Portland OR)

Most people do not need to go to the expense of buying a UV. A toilet brush is a lot cheaper and easier.

Carpet algae on the liner uses up nutrients that worse algae like string and "pea soup" algae feed on. Scrub it all off and you can end up with pea soup which is worse than string algae.

It also provides food for fish and wildlife and makes the liner look less artificial.

Striving to keep a pond completely free of algae is futile and causes stress instead of enjoyment. The thought that algae in a pond is "dirty" or "wrong" or "bad" is mistaken. Sure, there can be too much and can be problems but many people are totally stressed about normal healthy amounts.

    Bookmark   June 6, 2011 at 12:37PM
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newgen(9 Central California)

buyorsell: in that link you posted, I read that tadpoles eat algae, and I have thousands of them. Hopefully they'll keep it under control.

    Bookmark   June 6, 2011 at 3:41PM
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newgen, just wanted to completely support buyorsell. I mainly use my toilet brush to GRAB algae, but I also use it to scrub algae off of some rock surfaces where water spills. I often don't mind the algae color, but it often changes the spill pattern. In any case, I wasn't suggesting that you scrub the liner, although that was mainly due to my interest in hiding the liner and lazyness.

I had not considered the competition of algaes, but it sounds plausable. I have never had pea soup problems. My worst difficulty was a buildup of some fuzzy crud on underwater plants that made them look filthy. Perhaps that was an algae, because it has been gone for two years since my other plants in the pond and long stream have really gotten established. The plants keep nitrogen levels under control (perhaps over control since my lilly flower production is down) and the massive root systems catch gobs of crud. My total pond system is a pump, the stream, a small Skippy Filter that doesn't seem to catch anything (I suspect the stream is doing ALL filtering), and the toilet brush. Very low tech!

    Bookmark   June 7, 2011 at 9:31AM
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buyorsell888(Zone 8 Portland OR)

Not my link but Tadpoles and Toadpoles ;) DO eat algae. So do goldfish and koi. Not enough to keep a pond pristine though....

    Bookmark   June 7, 2011 at 12:15PM
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newgen(9 Central California)

The algae keeps getting sucked up into my filter, and slowing/impeding the water spray head. THAT is my main concern. Every few days, I have to pull out string algae from the inlet of the filter box, I've adjusted the inlet opening to be as small as possible, so as to minimize that amount of algae that can get sucked in. Previously, the filter box was placed on the bottom of the pond (about 3' deep), too much algae "suckage", so I relocated it to the "shelf" of the pond. Now it's much shallower (less than a foot deep), so of course it can't filter the deep water and the algae down there, but there's enough algae floating around near the surface to cause blockage.

    Bookmark   June 7, 2011 at 12:48PM
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buyorsell888(Zone 8 Portland OR)

We have a DIY filter made of one of those plastic mesh pots for aquatic plants filled with plastic scrubbies connected to the intake on our pump so the filter can get clogged but not the pump.

If you have loose algae floating around you can use quilt batting to capture it too

    Bookmark   June 8, 2011 at 11:24AM
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rsingley(z6a NJ)

Excess algae is caused by excess nutrients. If you limit the nutrients you limit the algae growth. You can add hydrogen peroxide, if you choose, or you can modify your pond "system" to handle the nutrients. In the past I added a small haybale as soon as the ice thawed. The haybale decomposes and releases hydrogen peroxide which impedes the growth of filamentous algae. I had some, but not very much string algae and it usually disappeared fairly quickly, but then I had a suspended algae bloom(pea soup as someone referred previously).

In an effort to provide very early spring vegetation for the local tree frog population I added 3 marsh marigold plants to my 900 gallon pond. Although they did not help in attracting frogs, they did absorb the excess nutrients very early in the season before the filamentous algae or the suspended algae began to develop and I haven't had an outbreak since.

At this point I do not add any chemicals, haybales or other algae control agents and have nothing but crystal clear water. When temps are appropriate I add a few water hyacinths which are another fantastic, natural filter that carries on the nutrient absorption when the marsh marigolds go dormant in the heat of the summer.

Good luck

    Bookmark   June 10, 2011 at 6:48AM
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Hi. I have a 2500 gallon pond and have raised koi and goldfish for years. Alage can be a battle espically string alage. I suggest building a pergula or shade over the pond and this will cut out your alage problem.if you are raising fish NEVER use an alagecide because it cuts the avaiable oxygen in half for the fish and can kill them. It certainly makes it harder for them to breathe! I've found the pergula to be the very best choice. It has cut my alage in half and the fish love it! It also looks very nice. Direct sun is the cause of alage.a nice pergula (shade structure) makes all the difference in the world! This is advice I live by. My fish are happy my pond is clear and my alage is no longer out of control! There will always be alage on the sides of the pond but the floating ugly green clumps of fillimounious alage are a thing of the past! If the pond continues in the direct sun the alage will continue to grow back.I had learned this the hard way after many years of pond keeping. My pegula has a lattuce roof allowing light to come through but not enough to cause an alage problem. We built ours by hand and it was up in one day. They are not expensive to build and they are very worth it! I have a large pond so my structure had to be larger and still it was only about 150 dollars in materials. If you have a small pond you can do it for about50 dollars! Good luck and happy ponding!

    Bookmark   June 12, 2011 at 1:52PM
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MaeT(z5 NL, Canada)

Do you have pictures of your pergola that you can post. I am considering doing something like that. We are constructing a privacy wall behind the pond and might be able to extend from that.

    Bookmark   June 12, 2011 at 4:30PM
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